Astronomy and astrophysics rely heavily on computer modeling, but being neither a physicist nor computer scientist, I cannot relate to the term "computer model." What is such a model, and how do scientists build one?

This is easiest to explain by an example. Suppose we launch a spacecraft from Earth and want to calculate its trajectory thereafter. Newton’s laws of motion and gravitation govern the probe. These laws are mathematical formulas that take as input the current position of the spacecraft and return as output the rate at which its velocity (meaning both its speed and direction) changes in response to the gravity of the Sun, Earth, other planets, and any other objects with mass.

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